On the relationship between the multi-antenna secrecy communications and cognitive radio communications

  • Authors:
  • Lan Zhang;Rui Zhang;Ying-Chang Liang;Yan Xin;Shuguang Cui

  • Affiliations:
  • Department of Electrical and Computer Engineering, National University of Singapore and Institute for Infocomm Research, A*STAR, Singapore;Institute for Infocomm Research, A*STAR, Singapore and Department of Electrical and Computer Engineering, National University of Singapore;Institute for Infocomm Research, A*STAR, Singapore;NEC Laboratories America, Princeton, New Jersey;Department of Electrical and Computer Engineering,Texas A&M University, Texas

  • Venue:
  • IEEE Transactions on Communications
  • Year:
  • 2010

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Abstract

This paper studies the achievable rates of the multi-antenna or multiple-inputmultiple-output (MIMO) secrecy channel with multiple single-/multi-antenna eavesdroppers. By assuming Gaussian input, the maximum achievable secrecy rate is obtained with the optimal transmit covariance matrix that maximizes the minimum difference between the channel mutual information of the secrecy user and those of the eavesdroppers. The maximum secrecy rate computation can thus be formulated as a non-convex max-min problem, which cannot be solved efficiently by existing methods. To handle this difficulty, this paper explores a new relationship between the secrecy channel and the recently developed cognitive radio (CR) channel, in which the secondary user transmits over the same spectrum simultaneously with multiple primary users, subject to the received interference power constraints at the primary users, or the so-called "interference temperature (IT)" constraints. By constructing an auxiliary multi-antenna CR channel that has the same channel responses as the secrecy channel, this paper shows that the optimal transmit covariance to achieve the maximum secrecy rate is the same as that to achieve the CR spectrum sharing capacity with properly selected IT constraints. Thereby, finding the optimal complex transmit covariance matrix for the secrecy channel becomes equivalent to searching over a set of real IT constraints in the auxiliary CR channel. Based on this relationship, efficient algorithms are proposed to solve the non-convex secrecy rate maximization problem by transforming it into a sequence of convex CR spectrum sharing capacity computation problems, under various setups of the secrecy channel.